注意：默认值只能在界面初始化直接中设置

DataGridViewComboBoxColumn dataGridViewComboBoxColumn = new DataGridViewComboBoxColumn();
dataGridViewComboBoxColumn.Name = "dgvcbcSeatType";
dataGridViewComboBoxColumn.DataPropertyName = "SeatType";
dataGridViewComboBoxColumn.DataSource = this.getSeatTypies();
dataGridViewComboBoxColumn.ValueMember = "key";
dataGridViewComboBoxColumn.DisplayMember = "value";
dataGridViewComboBoxColumn.HeaderText = "席别";
dataGridViewComboBoxColumn.Width = 100;
this.dgvOrder.Columns.Add(dataGridViewComboBoxColumn);

数据源：

        private List<KeyValuePair<string, string>> getSeatTypies()
        {
            return new List<KeyValuePair<string, string>>
            {
                new KeyValuePair<string, string>("0", "无座"),
                new KeyValuePair<string, string>("1", "硬座"),
                new KeyValuePair<string, string>("2", "软座"),
                new KeyValuePair<string, string>("3", "硬卧"),
                new KeyValuePair<string, string>("4", "软卧"),
                new KeyValuePair<string, string>("6", "高级软卧"),
                new KeyValuePair<string, string>("9", "商务座"),
                new KeyValuePair<string, string>("7", "一等软座"),
                new KeyValuePair<string, string>("8", "二等软座"),
                new KeyValuePair<string, string>("M", "一等座"),
                new KeyValuePair<string, string>("O", "二等座"),
                new KeyValuePair<string, string>("P", "特等座")
            };
        }